The present invention relates to a double row tapered roller bearing apparatus which is adapted to support, for example, a pinion shaft constituting a differential gear for a motor vehicle in a cantilever manner so as to freely rotate in a housing.
Conventionally, there has been proposed a double row tapered roller bearing apparatus of this type as shown in FIG. 5. This double row tapered roller bearing apparatus includes a double row tapered roller bearing 100 adapted to support a pinion shaft 110 having a pinion 122 which is in mesh with a ring gear, in a cantilever manner with respect to a housing 111. This double row tapered roller bearing 100 includes a row of conical rollers 101 located inwardly in an axial direction, and a row of conical rollers 102 located outwardly in an axial direction. The row of the conical rollers 101 is arranged between a first inner ring 103 and a first track face of an integral outer ring 105, while the row of the conical rollers 102 is arranged between a second inner ring 107 and a second track face of the integral outer ring 105. An outer peripheral face of this integral outer ring 105 is engaged with and fixed to an inner peripheral face of an opening in the housing 111, and inner peripheral faces of the first and second inner rings 103, 107 are engaged with and fixed to an outer peripheral face of the pinion shaft 110.
The integral outer ring 105 includes through holes 112 and 113 which extend from its inner peripheral face between the first track face and the second track face and pass through its outer peripheral face. This through hole 112 enables a space in the bearing between the row of the conical rollers 101 and the row of the conical rollers 102 to communicate with an upper space in the housing 111 by way of a channel 123. In the same manner, the through hole 113 enables the space in the bearing to communicate with a lower space in the housing 111 by way of a channel 115 in the housing 111.
A hub 116 is engaged with and fixed to the pinion shaft 110 adjacent to an end face of the second inner ring 107. A seal member 121 is engaged between the hub 116 and the integral outer ring 105.
In this double row tapered roller bearing apparatus, the pinion 122 is caused to rotate with a rotation of the pinion shaft 110 which is pivotally supported by the double row tapered roller bearing 100 with respect to the housing 111, and the ring gear (not shown) which is in mesh with this pinion 122 will rotate.
This rotating ring gear scrapes up lubricating oil which has been stocked at a determined level in the lower space in the housing 111, and supplies the lubricating oil from the upper space into the space in the bearing by way of the channel 123 in the housing 111 and the through hole 112 in the outer ring 105. This lubricating oil supplied into the space in the bearing is then supplied to the row of the conical rollers 101 adjacent to the pinion and the row of the conical rollers 102 adjacent to the opening thereby to lubricate the double row tapered roller bearing 100. This lubricating oil which has been supplied to the double row tapered roller bearing 100 is returned to the lower space by way of the row of the conical rollers 101. Further, the lubricating oil is returned to the lower space by way of the through hole 113 in the integral outer ring 105 and the channel 115 in the housing 111.
By the way, a blind space N is constituted by a combination of an outer peripheral face 107A of a large diameter end of the second inner ring 107, an inner peripheral face 105A of an end part of the integral outer ring 105, and the seal member 121. As the results, a flow of the lubricating oil from the upper through hole 112 to the row of the conical rollers 102 located outwardly in the axial direction is blocked, or the lubricating oil staying in the blind space N is deteriorated, and hence, defective lubrication may occur.
For example, in case where a spread of the lubricating oil from the aforesaid ring gear has been decreased, the supply of the lubricating oil from the upper through hole 112 is decreased, and there is such a probability that a shortage of lubrication may occur at the outward row of the conical rollers 102. Specifically, with respect to the inward row of the conical rollers 101, because a space between the inner ring 103 and the outer ring 105 interposing this inward row of the conical rollers 101 is open toward the space in the housing 111, even though the supply of the lubricating oil to the aforesaid through hole 112 has become poor, the inward row of the conical rollers 101 is easily supplied with the lubricating oil, as compared with the outward row of the conical rollers 102, and a shortage of the lubricating oil will rarely happen. In contrast, the outward row of the conical rollers 102 is likely to be short of the lubricating oil, since a space between the inner ring 107 and the outer ring 105 interposing this outward row of the conical rollers 102 is blocked with the seal member 121. Particularly, in case where the ring gear and the pinion 122 constitute a differential gear for a vehicle, a splash of the lubricating oil by the ring gear may sometimes be lost depending on a posture of the vehicle or a lateral G (an acceleration), and the row of the conical rollers 102 adjacent to the opening may be burned in.
As a double row tapered roller bearing to be incorporated in a bevel gear, for example, and adapted to rotatably support a power transmitting shaft thereof, there has been a type including a single outer ring having two rows of outer ring tracks in a conical shape and integrally formed as a whole. In such a bearing of the type having the integral outer ring, it has been proposed that lubricating oil is supplied to a rolling contact area between the inner and outer ring tracks and the conical rollers by way of a lubricating hole which is provided in a laterally middle part of the above mentioned outer ring.
By the way, in the conventional double row tapered roller bearing as described above, an amount of the lubricating oil to be supplied to an interior of the bearing has been regulated according to a length of the conical rollers and so on. A diameter of a mouth of the above mentioned lubricating hole has been determined on the basis of this amount of the lubricating oil, and the lubricating hole has been formed by drilling work employing a drill or the like. However, in this bearing, as shown in FIG. 6 for example, it has sometimes happened that depending on an interior shape of the bearing, a part of a mouth 51a of a lubricating hole 51 on an inner periphery of an outer ring 50 may intersects an outer ring track 50a which is formed on the outer ring 50. For this reason, in case where burrs or fins have occurred when the lubricating hole 51 is formed by the drilling work, these burrs or fins may sometimes project from the outer ring track 50a, and when the bearing has been assembled, the burrs or fins may be caught between the conical rollers and the outer ring track 50a. As the results, there has arisen such a problem that a surface of the outer ring track 50a may be damaged and life of the bearing may be decreased.
Although there has been an idea of conducting a step for removing the burrs or fins after the above mentioned drilling work, effecting such a removing step will incur a new problem that production steps of the bearing may be increased, which will result in a rise of cost for the bearing.